Method for manufacturing a screen cylinder



United States Patent Office 3,354,519 Patented Nov. 28, 1967 METHOD FOR MANUFACTURING A SCREEN CYLINDER Lodewijk Jansen, St. Anthonis, Netherlands, assignor to Gebroed'ers Stork & Cos Apparatenfabriek N.V., Amsterdam, Netherlands, a limited-liability company No Drawing. Filed Oct. 12, 1965, Ser. No. 502,813 Claims priority, application Netherlands, Oct. 15, 1964, 6411,984 2 Claims. (Cl. 29148.4)

ABSTRACT OF THE DISCLOSURE A screen cylinderfor a screen printing machine formed by precipitating nickel on a copper alloy cylinder, removing the resulting tubular nickel layer and mounting the same on a cylinder of heat resistant material, the nickel cylinder is then perforated in a helical pattern by a heated needle For printing textile-, plasticand paper webs two methods have been generally utilised:

(1) So called rouleau-printing, that is to say the application of engraved copper cylinders;

(2) So called fiat-printing, in which process a screen is used which consists of a flat tensioned gauze.

The possibility of applying rouleau-printing is rather limited, the process of engraving copper cylinders being moreover expensive and much craftmanship being required therefor. Such cylinders, because of their heavy weight, are hard to be handled and the interchange of these cylinders on a rouleau-printing machine is time consuming. From the economical view point this method is only justified for great lengths. The required high working pressure causes loss of brightness and brilliance.

The fiat screen printing method is, however, disadvantageous in that it involves an intermittent movement so that a fast rate of production cannot be achieved. Moreover it is almost impossible to print continuous coloured surfaces such as lengthwise extending stripes and the like. Difficulties are sometimes experienced in that the screen sticks to the web, so that because of these disadvantages this fiat screen printing method is practically exclusively applied to short special lengths of relatively high quality material of high cost price.

During recent years a third method has been developed which is based on the above-mentioned flat-printing method. This process is the so called rotation screen printing with cylindrical stencils. This new process is very attractive, but so far no satisfactory solution has been found for manufacturing a screen cylinder as basic element (a so-called blank) for making a cylindrical stencil thereof. Hitherto these cylinders were made by winding up a flat piece of metal gauze. Such a cylinder shows, however, a weld which always remains visible even if the gauze is galvanically stiffened. From the print-technical view point these guaze cylinders are disadvantageous in that they can exclusively be made of coarse gauze kinds, the said cylinders owing to the galvanic stiffening moreover becoming thick to an extent such that their field of application is limited to very coarse fabrics and patterns (bathing cloth and the like).

Attempts have been made to develop a method for manufacturing a screen cylinder in which the starting point is not a flat piece of gauze. This method consists in that one starts from a thin walled copper cylinder in which is etched a screen pattern, so that the pattern is constituted by individual holes. This etched copper cylinder is thereupon galvanically stiffened in order to obtain the required solidity. This process is, however, not workable, since it is not only complicated and expensive but moreover disadvantageous in that the screen becomes too thick for its application to a thin non absorbing material. To this it may be added that the gauze cylinders made in this way show the same important disadvantage as the engraved copper cylinders, viz., that the cylinder can only be used once.

It is an object of the invention to provide a method for the manufacture of a screen cylinder as basic element or blank gor making thereof a cylindrical stencil for a screen printing machine, said method avoiding the abovementioned disadvantages. According to the invention this object is attained by incorporating the following steps into the new method:

(a) Electrolytical precipitating of nickel on a cylinder of a copper alloy such that there is a perceivable difference of the coefiicient of thermal expansion between the deposited nickel layer and the cylinder;

(b) modifying the temperature of the cylinder with the nickel layer in such a way that the nickel layer loosens like a cuff from the cylinder and is thereupon slid therefrom;

(c) mounting of the nickel cuff on a cylinder of heat resistant, resilient, material like nylon;

(d) perforating according to a helical pattern of the material of the nickel cuff, the perforation being carried out by means of a heated needle.

The wall thickness of the cylinder made in this way is entirely independent of the fineness of the perforation, but this thickness of wall should be over 0.06 mm. in order to obtain a sufficient stiffness and life time.

In order to make a cylindrical stencil of this screen cylinder a design should be provided on the cylinder which can be effected in a simple way. For that purpose the cylinder is covered with a light-sensitive lacquer kind, whereupon by means of a light source the design is photographically transferred to the cylinder. At the location of the design the lacquer remains unexposed and therefore soluble. After lighting each unexposed portion can be removed by simply washing the cylinder, whereupon the cylindrical stencil is ready for use.

The important advantages of the method according to the invention are as follows. Due to the very small wall thickness of the cylinder the quantity of color paste to be applied is limited to a minimum required for printing t-hin, non absorbing, stocks. The latter circumstance is independent of the fineness of the perforation and the dimension of the individual holes. Through the holes of the stencil the color paste is pressed outwardly from the inner side by means of a doctor. When the angle enclosed between this doctor and the cylinder wall is the quantity of paint applied is exclusively determined by the wall thickness of the cylinder, while the applied quantity of color paste becomes larger accordingly as this angle is smaller. In this way with one and the same cylinder both extremely thin and very coarse fabrics can be printed over, while maintaining fully the required quality, and this can be done without modification of the composition of the color paste.

A further advantage of the method according to the to the invention is that a cylinder is obtained which is capable of being used several times that is to say with a different design. This design can be photographically applied via a lacquer layer and after use be removed, so that the base cylinder is thereafter available for a new design. This repeated use is not possible with a screen cylinder provided With an etched design.

The method according to the invention is preferably performed such that the holes in the nickel cuff are provided through a needle having a square cross section, care should be taken that the pitch of the helical pattern is equal to the sum of the dimension of the hole and the distance between two consecutive holes. A very uniform pattern is hereby obtained which in all directions shows the same permeability.

The selection of the fineness of perforation which for instance can be 60, 80 or 100 mesh gauge is independent of the nature of the material to be printed and is exclusively determined by the fineness of the design to be provided.

It will be understood that the present invention is susceptible to modification in order to adapt it to different usages and conditions and, accordingly, it is desired to comprehend such modification within this invention as may fall within the scope of the appended claims.

What is claimed is:

1. A method for manufacturing a screen cylinder as basic element for making thereof a cylindrical stencil for a screen printing machine said method comprising the following steps:

(a) eleetrolytical precipitating of nickel on a cylinder of a copper alloy such that there is a perceivable difference in the coefiicient of thermal expansion between the deposited nickel layer and the cylinder;

(b) modifying the temperature of the cylinder with the nickel layer in such a way that the nickel layer loosens like a cuff from the cylinder and is thereupon slid therefrom;

(c) mounting of the nickel cuff on a cylinder of heat resistant, resilient, material like nylon;

(d) perforating according to a helical pattern of the material of the nickel cufi, the perforation being carried out by means of a heated needle.

2. A method according to claim 1, characterized in that the holes in the nickel cuff are provided through a needle having a square cross section, the arrangement being such that the pitch of the helical pattern is equal to the sum of the dimension of the hole and the distance between two consecutive holes.

References Cited UNITED STATES PATENTS THOMAS H. EAGER, Primary Examiner.

Brous et al 29-423 

1. A METHOD FOR MANUFACTURING A SCREEN CYLINDER AS BASIC ELEMENT FOR MAKING THEREOF A CYLINDRICAL STENCIL FOR A SCREEN PRINTING MACHINE SAID METHOD COMPRISING THE FOLLOWING STEPS: (A) ELECTROLYTICAL PRECIPITATING OF NICKEL ON A CYLINDER OF A COPPER ALLOY SUCH THAT THERE IS A PERCEIVABLE DIFFERENCE IN THE COEFFICIENT OF THERMAL EXPANSION BETWEEN THE DEPOSITED NICKEL LAYER AND THE CYLINDER; (B) MODIFYING THE TEMPERATURE OF THE CYLINDER WITH THE NICKEL LAYER IN SUCH A WAY THAT THE NICKEL LAYER LOOSENS LIKE A CUFF FROM THE CYLINDER AND IS THEREUPON SLID THEREFROM; (C) MOUNTING OF THE NICKEL CUFF ON A CYLINDER OF HEAT RESISTANT, RESILIENT, MATERIAL LIKE NYLON; (D) PERFORATING ACCORDING TO A HELICAL PATTERN OF THE MATERIAL OF THE NICKEL CUFF, THE PERFORATION BEING CARRIED OUT BY MEANS OF A HEATED NEEDLE. 